Data

The logging data was recorded by Schlumberger in DLIS format. Data were processed at the Borehole Research Group of the Lamont-Doherty Earth Observatory in February 2009.

Logging Runs

Tool string	Pass	Top depth (mbsf)	Bottom depth (mbsf)	Pipe depth (mbsf)	Notes
DIT/HLDS/GPIT/HNGS	Downlog	0	518	99	No source on HLDS
DIT/HLDS/GPIT/HNGS	Main	0	555	96	No source on HLDS
DIT/HLDS/GPIT/HNGS	Repeat	450	555		No source on HLDS
FMS/GPIT/HNGS	Pass 1	137	525
FMS/GPIT/HNGS	Pass 2	137	520
MSS/HLDS/GPIT/HNGS	Main	97.5	469		No source on HLDS
MSS/HLDS/GPIT/HNGS	Repeat 1	277	475		No source on HLDS
MSS/HLDS/GPIT/HNGS	Repeat 2	583	473		No source on HLDS. Caliper closed.

Logging opeartions started with the DIT/HLDS/GPIT/HNGS string which recorded data downlog first and then uplog on a main and repeat run. During the repeat the wireline winch experienced some technical difficulties which eventually required the closing of the caliper from 3335 to 3280 mbrf (523-468 mbsf) to prevent possible damage. No problems were encountered during the main run of the DIT/HLDS/GPIT/HNGS string. The FMS/GPIT/HNGS tool string encountered significant bridges, which prevented it from reaching total depth.

The new MSS sonde was run three times, delivering a main run and two repeat sections. The caliper was kept open during the first reapeat and closed during the second one.

The WHC was used and tested throughout logging operations.

The depths in the table are for the processed logs (after depth shift to the sea floor and depth matching between passes). Generally, discrepancies may exist between the sea floor depths determined from the downhole logs and those determined by the drillers from the pipe length. Typical reasons for depth discrepancies are ship heave, wireline and pipe stretch, tides, and the difficulty of getting an accurate sea floor from a 'bottom felt' depth in soft sediment.

Processing

Depth shift to sea floor and depth match. The original logs were first shifted to the sea floor (- 2812 m). The sea floor depth was determined by the step in gamma ray values at 2812 mbrf on the DIT/HLDS/GPIT/HNGS logs . This differs by 4 m from the sea floor depth given by the drillers (2816 mbrf). Then the depth-shifted DIT/HLDS/GPIT/HNGS main run has been depth-matched to the first pass of the FMS/GPIT/HNGS tool string using the caliper log, because of the low signature and poor correlation of the gamma ray logs. For the same reason, the DIT/HLDS/GPIT/HNGS downlog has been depth-matched to the main run using the resistivity logs. Neither the FMS/GPIT/HNGS Pass 2 or the repeat of the DIT/HLDS/GPIT/HNGS logs needed depth-matching. The main run of the MSS/HLDS/GPIT/HNGS was depth-matched to the reference FMS/GPIT/HNGS using the caliper logs. The two repeats of the MSS were then matched to the main MSS using the susceptibility curves (low resolution sensor).

Depth matching is typically done in the following way. One log is chosen as reference (base) log (usually the total gamma ray log from the run with the greatest vertical extent and no sudden changes in cable speed), and then the features in the equivalent logs from the other runs are matched to it in turn. This matching is performed manually. The depth adjustments that were required to bring the match log in line with the base log are then applied to all the other logs from the same tool string.

Environmental corrections. The HNGS was corrected for hole size during the recording.

Magnetic susceptibility data. The magnetic susceptibility toold was run for the first time during Expedition 320T. At the time of this processing the recorded data has not been calibrated yet and therefore is not presented in ASCII file format in the online database. It will be included at a later date.

Quality Control

The quality of the data is assessed by checking against reasonable values for the logged lithologies, by repeatability between different passes of the same tool, and by correspondence between logs affected by the same formation property (e.g. the resistivity log should show similar features to the sonic velocity log).

The good correlation between the different runs suggests that the wireline heave compensator performed well.

Despite the lack of calibration of the susceptibility log, there is good correlation between the three passes. More processing in required to produce final results.

Gamma ray logs recorded through bottom hole assembly (BHA) and drill pipe should be used only qualitatively, because of the attenuation of the incoming signal. The thick-walled BHA attenuates the signal more than the thinner-walled drill pipe.

Hole diameter was recorded by the hydraulic caliper on the HLDS tool (LCAL) and by the FMS tool (C1 and C2). The caliper was closed from 3335 to 3280 mbrf (523-468 mbsf) during the DIT/HLDS/GPIT/HNGS downlog and repeat run and during the MSS/HLDS/GPIT/HNGS second repeat run.

A null value of -999.25 may replace invalid log values.

Additional information about the drilling and logging operations can be found in the Operations and Downhole Measurements sections of the expedition reports, Proceedings of the Integrated Drilling Program, Expedition . For further questions about the logs, please contact:

Cristina Broglia

Phone: 845-365-8343

Fax: 845-365-3182

E-mail: Cristina Broglia